Real Unión Irún

Real Unión were among the early pioneering Spanish football teams and, along with fellow Basque clubs Athletic Bilbao, Real Sociedad and Arenas Club de Getxo were founding members of La Liga, in 1928. The club was formed in 1915 following the merger of Irún Sporting Club and Racing Club de Irún. The former was founded in 1902 as Irún Foot-Ball Club, changing its name in 1907. The latter, formed in 1908, had already won the 1913 Copa del Rey, beating Athletic Bilbao 1–0 in a replayed final. The club was briefly known as Unión Club Irún before Alfonso XIII gave the club royal approval, but during the Second Spanish Republic the club reverted to this name.

Real Unión then won the Copa del Rey a further three times, beating Real Madrid in 1918 and again in 1924 (with former Derby County and England striker Steve Bloomer acting as their coach). In 1927 they defeated Arenas Getxo in the first all-Basque final. The latter two finals both ended in 1–0 victories, with José Echeveste netting the winner on both occasions. In 1922 they were runners-up, losing 5–1 to FC Barcelona. In 1930 they participated in the Coupe des Nations in Geneva, Switzerland, a predecessor of the UEFA Champions League since the champions of all major European football nations were invited, although it has never been entirely clear why Unión was invited as they had finished sixth in the 1929–30 La Liga. Nonetheless, they were eliminated in the quarter-finals by Slavia Prague. The club was relegated from La Liga in 1932.

In 1920, when Spain made their international debut at the Olympic Games, the club provided the squad with two players—Eguiazábal and Patricio, the latter scoring Spain's first-ever goal in international football in a 1–0 victory over Denmark on 28 August 1920. Another Real Unión player, René Petit, took part in the same Olympic Games with France. In the 70s and 80s, Spanish internationals Javier Irureta and Roberto López Ufarte began their career with the club.

On 11 November 2008, in the 2008–09 Copa del Rey against Real Madrid, Real Unión lost 3–4 at the Santiago Bernabéu, but secured a famous aggregate victory following a 3–2 home victory in the first leg (away goals rule). It was the first time in history that Real Madrid were eliminated by a Segunda División B team at home.

The club finally returned to the Segunda División in 2009 after a 44-year absence, successively defeating CE Sabadell FC (2–1 aggregate) and AD Alcorcón (3–1) in the 2008–09 promotion play-offs. However, it would be a short-lived return, as the team was immediately relegated, after ranking 21st.

After a season in the Spanish second division, the team was relegated to the third division. In the 2010/11 season, they finished fourth in their group and entered the promotion playoffs. They lost the playoff tiebreaker to Sevilla Atlético after winning the first match 2-1 but losing the second 3-0. The 2011/12 season was inconsistent for Real Unión, and they finished 14th in the league. They finished eighth in 2012/13, and despite financial struggles in 2013/14, they managed to avoid relegation to the fourth division by finishing 15th.

In the 2014/15 season, the team was back fighting for promotion in the playoffs. Unfortunately, they were knocked out in the first round by UCAM Murcia. Murcia scored the winning goal in extra time of the second match – the first game at Stadium Gal had been a 0-0 draw. Despite this disappointment, the team bounced back strong and won the Copa Federación on April 16, 2015, after beating Castellón in a two-game final.